Draw data models for the following situations. In each case, think about the names you give each entity:

I. Farmers can own cows or share cows with other farmers.

II. A track and field meet can have many competitors, and a competitor can participate in more than one event.

III. A patient can have many physicians, and a physician can have many patients.

IV. A student can attend more than one class, and the same class can have many students.

V. The Marathoner, a monthly magazine, regularly reports the performance of professional marathon runners. It has asked you to design a database to record the details of all major marathons (e.g., Boston, London, and Paris). Professional marathon runners compete in several races each year. A race may have thousands of competitors, but only about 200 or so are professional runners, the ones The Marathoner tracks. For each race, the magazine reports a runners time and finishing position and some personal details such as name, gender, and age.